USB 1.0 specification USB 1.0 defined data transfer rates of 1.5 Mbps Low Speed and 12 Mbps Full Speed.
USB 1.1 was later released and Apple's iMac was the first mainstream product to use USB.
Following this, USB became a standard in the PC market.

USB 2.0 specification
USB 2.0 had a higher data transfer rate of 480 Mbps, which was 40x faster than USB 1.1.
While USB 1.1 only introduced connectors the size of type A and type B, USB 2.0 introduced
new connector options (Mini, Micro).

USB 3.0 specification
USB 3.0 data transfer rate had increased to 5.0 Gbps, decreased power consumption, increased
power output and was backward compatible with USB 2.0. It included a new, higher speed bus called
SuperSpeed in parallel with the USB 2.0 bus.

USB 3.1 specification
The USB group aimed to increase USB 3.0 data transfer rates to 10 Gbps. Hence, the USB 3.1
specification was created. Replacing the existing USB 3.0 SuperSpeed USB transfer rate, it was
also known as USB 3.1 Gen 1. Since introducing the faster transfer rate of 10 Gbps, it is
known as USB 3.1 Gen 2. It is backward compatible with USB 3.0 and USB 2.0.